How Long Will a 100Ah LiFePO4 Battery Last?

LiFePO4 batteries are available in many capacity ratings. The 100Ah battery is one of the most widely purchased among the different capacity options. 100 Ah rating batteries suit most users’ requirements, from motorhomes to solar panels.

Users of 100 Ah batteries always have one common question- ‘How long will a 100Ah battery last?’ This article will answer this question once and for all. Along with the answer, you will also learn about how you can calculate your battery lifespan yourself.

What is a LiFePO4 Battery?

A lithium iron phosphate battery is an improved form of conventional lithium-ion batteries. It is also known as an LFP battery. This type of battery has a lithium iron phosphate cathode and a graphite anode.

LiFePO4 batteries are known for their long cycle life and several other benefits over the alternative. LFP batteries last at least ten times longer than lead acid batteries. Benefits like these have replaced LFP batteries as the preferred choice for deep-cycle batteries.

LiFePO4 batteries outdo all their competitors, even based on the run time alone. Therefore, it is a good idea to use a LiFePO4 100Ah battery if run time is your concern. Users who switch from a traditional lithium battery to LiFePO4 often report over 20% increase in runtime.

How Long Will a 100Ah Battery Last?

LiFePO4 100 Amp hour battery can last anywhere from 5 days to half an hour. The exact duration of the running time depends on several factors discussed in the next section. The main parameter is the load you run on a 100 Ah battery.

The running time is inversely proportional to the applied load. A lower load would lead to a longer running time. For instance, a 10 W load can run the battery for five days (120 hours). A higher load will shorten the running time. A 1000W load will drain the battery in 72 minutes (1.2 hours).

What Factors Determine the Running Time of a 100Ah Battery?

Many factors at play decide how long will a LiFePO4 100Ah battery last. These factors are:

Battery Capacity

Battery capacity is the primary factor that determines its lifespan. The capacity of a battery is listed in Amp hours (Ah). We have specified the battery capacity to be 100 Ah in this situation. Therefore, this factor is preset and will not vary.

A larger capacity battery results in a longer running time, provided all other factors are constant. Therefore, if you were using a 200 Ah battery instead of 100 Ah, the running time would be twice as long.

Connected Load

Connected load is the next big parameter that determines the run time. The load is expressed in Wattage. The run time is inversely proportional to the number of watts connected to the battery.

Therefore, doubling the load would mean halving the run time. Similarly, slashing the load in half would mean doubling the runtime. For instance, consider the case where your 100 Ah battery is connected to a 1000 W load. You need a 200 Ah battery or a 500 W load if you want the battery to provide a double runtime.

Battery Condition

The condition is important to know how long will a 100ah battery last. It is common for LiFePO4 batteries to last over 5000 cycles. If you use a new battery, it will last as long as it ideally should. However, the runtime starts to lessen as the batteries deteriorate with time. The effect of battery condition on runtime is not as linear as the capacity or the load. However, the running time can be even 50% of the expected value for batteries at the end of their life.

The age of the battery does not solely determine the battery condition. The battery’s condition can deteriorate even after a year if it is not properly maintained and operated. Similarly, maintaining the battery ensures maximum running time even at the end of its expected life cycle.

Type of Battery

Many users are unaware that different types of batteries have varying runtime. This is true even for two batteries with the same ampere hours rating. The unequal running time comes due to a battery’s Depth of Discharge (DoD).

Depth of discharge refers to the degree to which you can discharge a battery. A lead acid battery has a depth of discharge of around 50%. Therefore, you will only get half of the expected running time from a lead acid battery before charging it again.

A lithium battery generally offers a depth of discharge of over 80%. The best in this regard is the LiFePO4 batteries. They offer a depth of discharge of 98% to 100%. Therefore, you get the entire expected runtime with a lithium battery. AGM batteries also have a low Depth of Discharge of around 80%.

Discharge Rate

The discharge rate of the battery is also called its C-rate. C-rate determines the maximum rate at which the battery should be discharged. As a general rule, the battery capacity is rated as 1C. A rate of 2C means that a discharge current of twice the capacity is possible, but with half running time. Similarly, a capacity of 0.5C means that a discharge rate of half the capacity is possible but with double the running time.

For instance, consider a 100Ah battery. A discharge rate of 1C would mean that the battery can provide a 100 A current for one hour. A discharge rate of 2C would mean that the battery can provide a 200 A current for 30 min. A discharge rate of 0.5C would mean that the battery can provide 50 A for 2 hours. The discharge rate of the battery is listed in the battery information. If the battery is discharged faster than this rate, the running time will be considerably shorter than expected.

Lead acid batteries are notorious for poor C-rate. Common values are 0.2C for 5 hour discharge and 0.05C for 20 hour discharge. However, for LiFePO4 batteries, the discharge rates of 3C and 5C are common. This means you can discharge lithium batteries at a higher rate without worrying about shortening the running time.

Self Discharge Rate

The self discharge rate of the battery becomes an important consideration if the battery undergoes a storage period. Self-discharge rate represents the amount of charge the battery loses even if it is not being used. This rate is more important for some batteries than the others.

For instance, a lead acid battery can self-discharge at the rate of 4% per week. Therefore, if you are not using a 50% charged battery for a week, you can expect the remaining charge to be around 46%. This means a reduced running time than expected. A change in running time can be noticed even if you are not using lead acid batteries for a couple of days.

For lithium batteries, the self discharge rate is quite low. LiFePO4 has a self-discharge rate of around 2% a month. Even if you are storing LiFePO4 batteries for multiple weeks, it will not affect the battery’s running time.

Temperature

The effect of temperature on the running time is not as drastic as the other factors above. However, this can change if the temperatures reach the extreme zone. At temperatures below -10°C, the running time of the 100Ah battery will be halved. The running time further decreases as the temperature dips in extremely cold weather. High temperatures do not harm the battery run time as long as it is within the manufacturer’s recommended range.

How long will a 100Ah battery last in cold weather?

A 100Ah battery will last for around 5 hours if running a load of 10A at -10 °C. This battery will last for 10 hours at a 10A load in the normal temperature range. There is also the possibility of malfunction when the temperature reaches extreme freezing conditions. You might have noticed this with car batteries when starting it in the winter. Fortunately, Eco Tree Lithium batteries have an inbuilt heater to combat this. Therefore, you get complete running time with heated batteries.

Calculating How Long Will a 100Ah Battery Last

It is easy to calculate how long will a 100Ah battery last for you. For calculations, you need to be aware of how the capacity is expressed. Let us go through these various expressions:

Watt-hours

Watt hours is the load in Watts that the battery can sustain for one hour. It is expressed as ‘Wh’. It is better to use Watt hours than Amp hours for calculating run time. This is because Watt hours provide a better representation of energy consumption. The appliances you use will have a Watts rating instead of an Ah rating. Therefore, calculating the Wh of the battery is useful.

To calculate Watt hours, multiply the Amp-hours by the battery voltage. Most deep-cycle batteries work on a 12 V system. The amp hours in this situation are already fixed to 100 amp hours. Therefore the watt hours for a 100ah battery will be:

Wh = Amp hours x Voltage

= 100 Ah x 12 V

= 1200 Wh

Depth of Discharge (DoD)

As discussed earlier, the DoD limits the fraction of energy that is usable. Therefore you can multiply the DoD by the Watt hours battery to know its usable power.

For instance, the DoD is just 50% for a lead acid battery. The usable battery capacity becomes:

Usable battery capacity for lead acid battery = Wh x DoD

= 1200 x 50%

= 600 Wh

In the case of LiFePO4 batteries, the DoD is 100%.

Usable battery capacity for LiFePO4 battery = 1200 x 100%

= 1200 Wh

Inverter Efficiency Rate (ER)

Batteries output DC power but users require AC. Therefore, an inverter is used to convert DC to AC. Some of the energy is lost in the conversion process. The amount of energy converted from the total energy is expressed with the Efficiency Rate (ER).

The net capacity is deducted by multiplying the usable battery capacity with the efficiency rate. Therefore,

Net Capacity = Usable capacity x ER

In the case of the 100 amp hours lead acid battery with a 95% ER inverter, the net capacity is:

= 600 Wh x 95%

Lead acid batteries Net capacity = 570 Wh

For a 100 amp hours LiFePO4 battery working with an inverter of 95% ER, the net capacity becomes

= 1200 x 95%

LiFePO4 Net capacity = 1140 Wh

Calculating the Running Time of the Battery

The running time calculation becomes very easy once you have the net capacity of the battery in Wh. You will need to add the Watt rating of every appliance you are using with the battery. For instance, if you are using a 50 W light and a 50 W speaker, the total load becomes:

Total Load= Sum of individual loads in W

= 50 W + 50 W

= 100W

The running time is the net capacity divided by the total load. Therefore,

Running Time = Net Battery Capacity ÷ Total Load

For the 100 amp hours lead acid battery, the running time becomes:

Running time (lead acid battery) = 570 ÷ 100

~ 5.7 hours or 342 minutes

For the LiFePO4 100 amp hour battery, the running time is:

Running time (LiFePO4) = 1140 ÷ 100

= 11.4 h or 684 minutes

Where to Find 100Ah LiFePO4 Battery?

Eco Tree Lithium is the leading supplier of LiFePO4 batteries. There are multiple options for a 100Ah battery with Eco Tree Lithium. Some of these lithium batteries even come with an inbuilt-heater and Bluetooth. The heater ensures that you can even start and use your battery in extreme conditions. This is much needed in LiFePO4 batteries, and no one else provides it. Bluetooth monitoring enables you to check your battery stats without opening the compartment.

Make sure to check the manufacturer’s warranty period regardless of where you buy your battery from. The warranty with the battery shows the manufacturer’s faith in its product. For instance, Eco Tree Lithium batteries come with a whopping 6-year warranty.

Conclusion

You can now calculate the running time for your LiFePO4 100Ah battery under any load. An important thing to note is the vast difference between the running time of LiFePO4 when compared with lead acid batteries. The running time alone is a good reason to switch to LiFePO4 batteries. Get in touch with Eco Tree Lithium to know more.